<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script src="https://cdn.staticfile.org/jquery/2.2.4/jquery.min.js"></script>
    <script>
     function radio(){
         var radio=$("[name='radio']:checked").val()
         alert("当前选中的radio控件的值"+radio)
     }
    </script>
    <input type="radio" name="radio" value="1" onclick="radio()" />
    <label>a</label>

    <input type="radio" name="radio" value="2" onclick="radio()" /><label>b</label>

    <input type="radio" name="radio" value="3" onclick="radio()" /><label>c</label>

    <input type="radio" name="radio" value="4" onclick="radio()" /><label>d</label>
</body>

</html>